The problems of exhaust gas pollution and high fuel consumption in internal combustion engines are well recognized today. One of the approaches for minimizing these problems is to design the engine for operation with a stratified charge. The definition of "stratified charge" is where the air-fuel mixture in the combustion chamber is not uniform and is generally very lean, with special provisions existing to ignite the mixture.
In a stoichiometric mixture of air and gasoline fuel (i.e., the air-gasoline mixture which is theoretically correct for proper combustion), the ratio by weight of air to gasoline is approximately 14.9:1. A charge having an air-fuel ratio leaner than 18:1 cannot be consistently ignited by a spark plug. Conventional carbureted or non-stratified charge engines operate generally with an air-fuel ratio in the range of 11:1 for a mixture which is richer than the ideal stoichiometric mixture to 16:1 for a mixture which is leaner than the ideal stoichiometric mixture.
Stratified charge engines with unrestricted air intake, however, have been successfully operated at the extremely low overall air-fuel ratios, for example, from the 20:1 to the 100:1 range.
Compared to engines operating in the approximately stoichiometric air-fuel ratio range, an engine operating on a leaner air-fuel ratio, as seen in FIG. 3, results in a significant reduction in both the oxides of nitrogen (NO.sub.x) and carbon monoxide in the engine exhaust and generally in some reduction of the hydrocarbons. In addition, there is normally a reduction in engine fuel consumption in a stratified charge engine having unrestricted air intake because of the lower pumping losses on the intake or suction stroke of the engine cycle due to the free flow of air into the combustion chamber.
The following U.S. Pat. Nos. are representative of patents showing internal combustion engines operating on the stratified charge principle:
2,484,009--Everett M. Barber--issued Oct. 11, 1949 PA1 2,595,915--Everett M. Barber--issued May 6, 1952 PA1 2,692,587--Everett M. Barber--issued Oct. 26, 1954 PA1 2,864,347--Everett M. Barber et al--issued Dec. 16, 1958 PA1 2,958,314--Edward Mitchell--issued Nov. 1, 1960 PA1 3,094,974--Everett M. Barber--issued June 25, 1963 3,924,598--Charles W. Davis--issued Dec. 9, 1975
Difficulty, however, has been experienced in operating stratified charge engines over an entire operating range while maintaining acceptable firing regularity and good engine performance.
Some prior art stratified charge engines and processes have required certain air flow patterns and fuel spray patterns in order to achieve regular firing. A number of the prior art patents show the use of a pilot fuel spray which is ignited by a spark plug to establish a flame which is used to ignite a main fuel spray, which requires that the main fuel spray be directed or oriented in a manner which causes the main fuel spray to properly contact the flame front established by the ignited pilot fuel spray.